The morphology and structure of ultradispersed polytetrafluoroethylene (UPTFE, FORUM trademark) samples after treatment with supercritical carbon dioxide (sc-CO2) were studied by physicochemical methods. It was shown that, in sc-CO2, low-molecular-weight fractions are dissolved and removed from pristine UFTFE. The structures of separated fractions were studied. With an increase in the dissolving power of sc-CO2 (by increasing pressure and varying temperature), the fractionation process gradually involves oligomers with higher molecular weights. (C) 2011 Elsevier B.V. All rights reserved.